The overall goal of this proposal is to define factors which are involved in bone destruction associated with inflammatory processes, especially periodontal disease. These factors will be assayed and their activity characterized in an in vitro model of bone resorption. Specific objectives can be summarized as follows: 1. Studies on bone resorption-stimulating factors derived from lymphocytes and other cells. Studies planned include isolation and characterization of osteoclast activating factor (OAF); characterization and comparison of OAF(s) produced by lymphocytes activated with various antigens and mitogens: and identification of the mononuclear cell responsible for OAF production. 2. Studies on direct effects of bacterial products on bone resorption. These studies include preparation and testing of cell wall materials from Actinomyces viscosus and other potential periodontal pathogens for direct stimulation of bone resorption. Active factors will be chemically characterized. 3. Bone resorbing activity in gingival tissue. Gingival tissue will be assayed for bone resorption-stimulating activity. Attempts will be made to correlate activity with the degree of tissue inflammation. 4. Effects of bone resorption-stimulating factors on bone in vivo. Studies will be done to develop an animal model for quantitative testing of the local effects on bone of materials studied in vitro.